PROJECT SUMMARY Unhealthy substance use (SU) is a leading cause of death and disability in the US and a common comorbidity of people living with HIV (PLWH), among whom it is consistently associated with delays to engagement in HIV care, worse retention in care, lower ART adherence, and worse viral and immunologic outcomes. Therefore, HIV research must use rigorous methods to account for SU in study designs and analyses and to test SU interventions. The Substance Use Research Core (SURC) is an innovative and defining feature of the Providence/Boston Center for AIDS Research (P/B CFAR) that will catalyze innovations in SU/HIV research and strengthen the P/B CFAR's mission to address HIV in vulnerable populations. To support the development of basic, clinical, and translational research that addresses the impact of SU on the HIV epidemic, the SURC has the following Specific Aims: 1) To provide CFAR investigators expertise in developing research projects that address gaps in SU/HIV priority issues both domestically and globally. The SURC will ensure that CFAR projects appropriately consider and incorporate the impact of SU on study outcomes; connect SU investigators and HIV investigators through formal and informal opportunities to develop collaborative projects; and work with CFAR investigators to formulate innovative and scientifically sound SU/HIV research questions. 2) To support CFAR investigators in the conduct of rigorous HIV research that takes SU into account. The SURC will provide services to help investigators identify the most appropriate tools to assess consumption, severity, consequences and associated stigma of SU as well as provide training on utilization of validated self-report scales, structured interviews, laboratory and ecological momentary assessments, and biological tests of SU. The SURC has expertise on SU pharmacotherapy, behavioral interventions, mobile health (mHealth) applications, and chronic disease management. Core services in this realm will include SU intervention selection and training, fidelity assessment techniques, intervention manuals, and adaptation to new populations. The SURC will also review relevant IRB protocols and provide guidance on ethical issues of particular importance to SU research, such as confidentiality protections and providing compensation to people actively using drugs. The services provided by the SURC will ensure that CFAR investigators are optimally equipped to pursue research projects that consider and address the major impact of SU on HIV prevention, the HIV Care Continuum, and HIV comorbidities.